Combination case heater and alarm circuit for refrigerators



Oct l, 1957 J. A. DAHLGREN 2,807,942

COMBINATION CASE HEATER AND ALARM CIRCUIT TCR REFRICERATCRS Filed Aug.4, 1955 Flai INVENTOR. JOHN A. DAHLGREN BTW HIS ATTORNEY United StatesPatent O COMBINATION 'CASEzHEATER AND ALARM CJRGUITFORsR1,311".Rlfll;RATORSSA 1 JohnrArDahlgren', Louisville, Ky., assignorto General Electric Company, ,a corporation of New York-- ApplicationAugust 4, 195s, serin-.Nq.sz6,41a

1 claim. (el, sz-89) The present' inventionfrelatesfto Ahollselloltirefrigerators and particularly yto a refrigeratedl `cabinet.V includingra storage; compartment for storing foodsA at-snb-freezingtemperatures.v

Household refrigerators and :freezers generallyconi-y prise,.an; outermetalV case-` andwan; innere liner insulated from the ,Case ,andfdeining'a Afoodfstorage compartment- Breaker. Strips extendinaaroundthe .accessonening'. to the linerbetweenthefliner and the outeryGaSegare employed to decrease thermalconduction betweenftheecaseand theliner but such insulating means have not been completelyelectivefziforrpreventingv condensation,y and; sweating of the outercase adjacenty the `access.opening Heat leakage` through the breakerstrip or the ,other ,insulating means, fromf the outercase'to theinterior of the` storage compartmentcausesthetemperature-of theoutencase tofall belowl lthe dew--pointv of the surrounding atmosphere.The condensed moisture-on the outer case causes discoloration anddeterioration of the case finish. To prevent such condensation, suitableheating means such as an electrical resistance heater have been employedto main tain the temperature of the case about the access openingsufficiently warm so that such condensation cannot occur.

It is also highly desirable, particularly in connection with homefreezers, to provide some sort of an alarm or indicator which will warnthe user of any abnormal rise in the storage compartment temperatureabove that at which the contents thereof can be safely stored. Forexample a blown fuse or similar power failure or failure of therefrigerating system, unless noted in time, will cause the temperatureof the storage compartment to rise to a point where the stored food willspoil.

Heretofore these two problems have been separately considered and,insofar as the construction of the refrigerator cabinet is concerned,separately solved. The present invention relates to and has as itsprincipal object the provision of a combination case heater and visualalarm circuit which not only requires fewer elements than are requiredif separate circuits were provided but also permits the use of lowercost and longer life elements with no loss in the elliciency andeffectiveness of the protective arrangement.

Further objects and advantages of the invention will become apparent asthe following description proceeds,

and the features of novelty which characterize the in vention will bepointed out with particularity in the claims annexed to and forming apart of this specification.

In carrying out the objects of the present invention, a refrigeratedcabinet is provided with an electric resistance rheater in heatingrelationship with the face portion of the refrigerator outer caseadjacent the access opening to the freezer compartment. The power supplyfor a low voltage lamp circuit which serves as a visual alarm, is tappedE the electric resistance heater. This alarm circuit is in series with aportion of the heater and in parallel connection with another portionthereof so that a low voltage long life lamp can be employed.Energization of the heater and visual alarm circuit is controlled by a2,807,942 Patented Oct.,` 1,; 1957.

2. single thermalv switch responsive to lthe temperatures within the:storage, compartmentA so-that\, any abnormal rise in thestoragecompartment tempBIaftureswill beindicated by d eenergizationfofthev Gircuit including ythe;alax'rn light. t

For a better understandingL of, the f invention Areference may be had tothe accompanying drawing in which:

Fig.v l isanelevational; view partly in sectionof a refrigeratedcabinet-showing schematicallyoneform of the present inventionV asembodied therein; and4 j Fig. 2 is an enlarged -fragmentarysectionaliview ytaken along the line 2-,2 lof Fig.;-l.

Referringtto the drawing there; is-shownv a refrigerated cabinetincludingan outer-y case 1 and -aniilner liner 2 forming afoodstorage.Vcompartment within the, cabinet. Afbrealrer strip `3 of suitable` heatinsulatingwmaterial bridges thelgap between the forward edge-4` of. the.`liner and the face-portion 5'of:thm-outercase.w The;.bre aker Strip 3extends entirelyl around-:theaccssszopening to. the Storace -Cgmpartmentformed bythe. liner -2 and maybeof any suitable. constructionandfmaterialadanted to thermal: ly insulate the fliner 2 from ,the-outercased. Suitable heat insulation I6 is also providdbetweenthe liner. and,the Outer easel A, verticalI dQor l7 isprovided for tclosinghe-accessopening to the; storage; compartment;y This l,door includes anedge.portion. 8` overlapping ,the face, portion 5 nf; the outer-*case and agasket 10 1engaging,1the,faceportioneS and sealingv the` spacebetweenVtheadoor ;andtl 1 e.,10uter case 1.

It will be understoodl ofcourse rthat'a suitablegrefrigerat: ingr-system(not shownlis provided tortmaintaining the space 4within the liner; 2at. suitableffood; preservationrtemperatures which in the case of thefreezer are ordinarily well below freezing. During operation of therefrigerating system due both to conduction and to convection currentswithin the space between the breaker strip 3 and the inner panel 11 ofthe door, there is a gradual cooling of the face portion 5 of the outercase to a point where moisture from the surrounding atmosphere condensesin this area of the cabinet.

In order to maintain the face portion of the outer case at temperatureswhich are sufliciently high to prevent this condensation, there isprovided electrical heating means in the form of a resistance heater 12which is preferably positioned within the space between the liner 2 andthe outer case 1 in heat exchange relationship with the face portion 5of the case. The positioning of the heater 12 is shown somewhatschematically in Figure l as extending along the two vertical sides ofthe cabinet adjacent the access opening to the storage compartment andsimilarly along the bottom of the cabinet. If desired the resistancewire may also extend along the upper face portion of the cabinetadjacent the access opening although the condensation problem with avertical or upright type cabinet is not as great in this area as in theremaining face portions of the outer case.

The resistance heater 12 is connected to a suitable source of power 14which in general will be the same source of supply as that used tooperate the refrigerating unit.

In accordance with the present invention there is pro vided a Visualalarm for indicating either power or refrigeration system failure. Thisalarm is in the form of a low voltage lamp 15 preferably positioned onthe front of the cabinet below the door 7 so as to be visible from infront of the cabinet to inform the user of the refrigerated cabinet asto whether or not the unit is operating properly. For this purpose thelamp is connected in series-parallel relationship with the heater andthe entire circuit including the heater 12 and the lamp 15 is controlledby a thermostat 16 which includes a switch 17, abellows 18 and a feelerbulb 19 positioned within the storage compartment and responsive to thetemperatures therein. During normal operation of the refrigeratingsystem serving the cabinet the switch 17 is closed so that heat iscontinuously supplied to the face portion 5 of the outer case and theindicator light is continuously illuminated. Upon either a refrigerationsystem failure or a power failure, both of which result in an increasein the temperature of the cabinet and opening of switch 17 controlled bybellows 18, the lamp circuit is de-energized so that the user is warnedof the failure by the fact that the light 15 is no longer illuminated.

By this arrangement in which the source of power for the indicator lightis tapped off a portion of the heater 12, any desired voltage andcurrent can be obtained for energizing the light 15 so that a lowvoltage bulb operating at lower than rated voltage and hence having along life can be employed in the alarm system. In order to provide thedesired voltage and current for the operation of the signal bulb 15, theresistance heater 12 preferably comprises one portion 21 in parallelwith the signal bulb circuit'and a second portion comprising thesections 22 and 23 in series connection with the lamp circuit.

From the foregoing, it will be seen that there has been provided asimple and low cost circuit including means for heating the outer caseof a refrigerated cabinet and for indicating power and refrigerationfailure.

The heater, as well as the indicator light, is energized only when thecabinet is at safe food preservation temperatures and does not supplyheat to the cabinet during periods of power or system failure, whichheat would accelerate the rate at which the cabinet and foodternperatures rise during such critical periods. By employing a portionof the heater as means for controlling the voltage and current suppliedto the signal bulb 15, a low voltage bulb can be employed as the visualalarm means without the use of additional resistances or transformermeans which would otherwise be required if the alarm circuit wereconnected directly to the normal power source. Furthermore less space isrequired in the cabinet structure for the alarm component of the circuitand as less heat is dissipated by the low voltage bulb, the bulb may beencased in or protected by a low cost decorative enclosure made ofplastic material or the like.

While there has been shown and described the specific embodiment of theinvention, it is not desired that the invention be limited to theparticular construction shown and described and it is intended by theappended claim to cover all modications within the spirit and scope ofthe invention.

What I claim as new and desire by Letters Patent of the United Statesis:

A refrigerated cabinet including an outer case, a liner insulated fromsaid case defining a food storage compartment having an access openingthereto, a door for closing said access opening including a portionengaging the face portion of said outer case about said access opening,and a combination case heater and visual alarm circuit comprising aresistance heater in heating relationship with said face portion of saidcase, a low voltage alarm light connected in parallel with a portion ofsaid resistance heater and in series with the remainder of said heaterand a thermal switch responsive to the temperature within said storagecompartment for controlling the energization of said circuit and adaptedto interrupt said circuit upon an abnormal rise in said temperature.

References Cited in the le of this patent UNITED STATES PATENTS2,400,168 Roach May 14, 1946 2,460,469 Rifkin Feb. 1, 1949 2,526,566Kolisch Oct. 17, 1950 2,535,278 Fletcher Dec. 26, 1950

